According to Official Guinness Records,
The most points scored by an individual in a professional ice hockey game is ten and is shared by Jim Harrison (b. July 9, 1947) (three goals, seven assists) for Alberta, later Edmonton Oilers in a WHA match at Edmonton on January 30, 1973, and by Darryl Sittler (b. September 18, 1950) (six goals, four assists) for Toronto Maple Leafs v. Boston Bruins in an NHL match at Toronto on February 7, 1976.
For a complete list of 1976 records, please visit 1976 Guinness Records in Canada.